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Observations of anthropogenic global warming

Archive for June, 2011

New research from last week 25/2011

Posted by Ari Jokimäki on June 27, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Positive cloud feedback possibly observed

Variations in cloud cover and cloud types over the ocean from surface observations, 1954–2008 – Eastman et al. (2011) “Synoptic weather observations from ships throughout the world ocean have been analyzed to produce a climatology of total cloud cover and the amounts of nine cloud types. About 54 million observations contributed to the climatology, which now covers 55 years, from 1954 to 2008. In this work interannual variation of seasonal cloud amounts are analyzed in 10-degree grid boxes. Long-term variations on the order of 5 – 10 years, coherent across multiple latitude bands, remain present in the updated cloud data. A comparison to coincident data on islands indicates that the coherent variations are probably spurious. An exact cause for this behavior remains elusive. The globally-coherent variations are removed from the grid-box time series using a Butterworth filter before further analysis. Before removing the spurious variation, the global average time series of total cloud cover over the ocean shows low-amplitude, long-term variations on the order of 2 percent over the 55-year span. High-frequency, year-to-year variation is seen on the order of 1-2%. Among the cloud types, the most widespread and consistent relationship is found for the extensive marine stratus and stratocumulus clouds (MSC) over the eastern parts of the subtropical oceans. Substantiating and expanding upon previous work, strong negative correlation is found between MSC and sea surface temperature (SST) in the eastern north Pacific, eastern south Pacific, eastern south Atlantic, eastern north Atlantic, and the Indian Ocean west of Australia. By contrast, a positive correlation between cloud cover and SST is seen in the central Pacific. High clouds show a consistent low-magnitude positive correlation with SST over the equatorial ocean. In regions of persistent MSC, time series show decreasing MSC amount. This decrease could be due to further spurious variation within the data. However, the decrease combined with observed increases in SST and the negative correlation between marine stratus and sea surface temperature suggests a positive cloud feedback to the warming sea surface. The observed decrease of MSC has been partly but not completely offset by increasing cumuliform clouds in these regions; a similar decrease in stratiform and increase in cumuliform clouds had previously been seen over land. Interannual variations of cloud cover in the tropics show strong correlation with an ENSO index.” Ryan Eastman, Stephen G. Warren, Carole J. Hahn, Journal of Climate 2011, doi: 10.1175/2011JCLI3972.1. [Full text]

Nature of forcing and climate state affect climate sensitivity

Dependency of Feedbacks on Forcing and Climate State in Physics Parameter Ensembles – Yoshimori et al. (2011) “Climate sensitivity is one of the most important metrics for future climate projections. In previous studies the climate of the last glacial maximum has been used to constrain the range of climate sensitivity, and similarities and differences of temperature response to the forcing of the last glacial maximum and to idealized future forcing have been investigated. The feedback processes behind the response have not, however, been fully explored in a large model parameter space. In this study, we first examine the performance of various feedback analysis methods that identify important feedbacks for a physics parameter ensemble in experiments simulating both past and future climates. The selected methods are then used to reveal the relationship between the different ensemble experiments in terms of individual feedback processes. We, for the first time, evaluate all the major feedback processes for an ensemble of paleoclimate simulations. It is shown that the feedback and climate sensitivity parameters depend on the nature of the forcing and background climate state. The forcing-dependency arises through the shortwave cloud feedback while the state-dependency arises through the combined water vapor and lapse-rate feedback. The forcing-dependency is, however, weakened when the feedback is estimated from the forcing that includes the tropospheric adjustments. Despite these dependencies, past climate can still be used to provide a useful constraint on climate sensitivity as long as the limitation is properly taken into account, because the strength of each feedback correlates reasonably well between the ensembles. It is, however, shown that our physics parameter ensemble does not cover the range of results simulated by structurally different models, which suggests the need for further study exploring both structural and parameter uncertainties.” Masakazu Yoshimori, Julia C. Hargreaves, James D. Annan, Tokuta Yokohata, Ayako Abe-Ouchi, Journal of Climate 2011, doi: 10.1175/2011JCLI3954.1.

Mankind controls the sediment flux to western Pacific Ocean

Recent changes of sediment flux to the western Pacific Ocean from major rivers in East and Southeast Asia – Wang et al. (2011) “The five largest rivers in East and Southeast Asia (Yellow, Yangtze, Pearl, Red and Mekong) are important contributors of terrigenous sediment to the western Pacific Ocean. Although they have annually delivered ~ 2000 × 109 kg of sediment to the ocean since 1000 yr BP, they presently contribute only ~ 600 × 109 kg/yr, which is reverting to a level typical of the relatively undisturbed watersheds before the rise in human activities in East and Southeast Asia at 2000 yr BP. During the most recent decades flow regulation by dams and sediment entrapment by reservoirs, as well as human-influenced soil erosion in the river basins, have sharply reduced the sediment delivered from the large river basins to the ocean. We constructed a time series of data on annual water discharges and sediment fluxes from these large rivers to the western Pacific Ocean covering the period 1950–2008. These data indicate that the short–term (interannual scale) variation of sediment flux is dominated by natural climatic oscillations such as the El Niño/La Niña cycle and that anthropogenic causes involving dams and land use control the long–term (decadal scale) decrease in sediment flux to the ocean. In contrast to the relatively slow historical increase in sediment flux during the period 2000–1000 yr BP, the recent sediment flux has been decreased at an accelerating rate over centennial scales. The alterations of these large river systems by both natural and anthropogenic forcing present severe environmental challenges in the coastal ocean, including the sinking of deltas and declines in coastal wetland areas due to the decreasing sediment supply. Our work thus provides a regional perspective on the large river–derived sediment flux to the ocean over millennial and decadal scales, which will be important for understanding and managing the present and future trends of delivery of terrigenous sediment to the ocean in the context of global change.” Houjie Wang, Yoshiki Saito, Yong Zhang, Naishuang Bi, Xiaoxiao Sun and Zuosheng Yang, Earth-Science Reviews, doi:10.1016/j.earscirev.2011.06.003.

Contrary to land-based wind farms, offshore farms cool their surroundings

Potential climatic impacts and reliability of large-scale offshore wind farms – Wang & Prinn (2011) “The vast availability of wind power has fueled substantial interest in this renewable energy source as a potential near-zero greenhouse gas emission technology for meeting future world energy needs while addressing the climate change issue. However, in order to provide even a fraction of the estimated future energy needs, a large-scale deployment of wind turbines (several million) is required. The consequent environmental impacts, and the inherent reliability of such a large-scale usage of intermittent wind power would have to be carefully assessed, in addition to the need to lower the high current unit wind power costs. Our previous study (Wang and Prinn 2010 Atmos. Chem. Phys. 10 2053) using a three-dimensional climate model suggested that a large deployment of wind turbines over land to meet about 10% of predicted world energy needs in 2100 could lead to a significant temperature increase in the lower atmosphere over the installed regions. A global-scale perturbation to the general circulation patterns as well as to the cloud and precipitation distribution was also predicted. In the later study reported here, we conducted a set of six additional model simulations using an improved climate model to further address the potential environmental and intermittency issues of large-scale deployment of offshore wind turbines for differing installation areas and spatial densities. In contrast to the previous land installation results, the offshore wind turbine installations are found to cause a surface cooling over the installed offshore regions. This cooling is due principally to the enhanced latent heat flux from the sea surface to lower atmosphere, driven by an increase in turbulent mixing caused by the wind turbines which was not entirely offset by the concurrent reduction of mean wind kinetic energy. We found that the perturbation of the large-scale deployment of offshore wind turbines to the global climate is relatively small compared to the case of land-based installations. However, the intermittency caused by the significant seasonal wind variations over several major offshore sites is substantial, and demands further options to ensure the reliability of large-scale offshore wind power. The method that we used to simulate the offshore wind turbine effect on the lower atmosphere involved simply increasing the ocean surface drag coefficient. While this method is consistent with several detailed fine-scale simulations of wind turbines, it still needs further study to ensure its validity. New field observations of actual wind turbine arrays are definitely required to provide ultimate validation of the model predictions presented here.” Chien Wang and Ronald G Prinn, 2011, Environ. Res. Lett. 6 025101 doi: 10.1088/1748-9326/6/2/025101. [Full text]

The ecosystems of clouds

Atmospheric cloud water contains a diverse bacterial community – Kourtev et al. (2011) “Atmospheric cloud water contains an active microbial community which can impact climate, human health and ecosystem processes in terrestrial and aquatic systems. Most studies on the composition of microbial communities in clouds have been performed with orographic clouds that are typically in direct contact with the ground. We collected water samples from cumulus clouds above the upper U.S. Midwest. The cloud water was analyzed for the diversity of bacterial phylotypes by denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene amplicons. DGGE analyses of bacterial communities detected 17-21 bands per sample. Sequencing confirmed the presence of a diverse bacterial community; sequences from seven bacterial phyla were retrieved. Cloud water bacterial communities appeared to be dominated by members of the cyanobacteria, proteobacteria, actinobacteria and firmicutes.” Peter S. Kourtev, Kimberly A. Hill, Paul B. Shepson and Allan Konopka, Atmospheric Environment, doi:10.1016/j.atmosenv.2011.06.041.

Carbon sink of European forests has increased

Reconstruction and attribution of the carbon sink of European forests between 1950 and 2000 – Bellassen et al. (2011) “European forests are an important carbon sink, yet the relative contributions to this sink of climate, atmospheric CO2 concentration ([CO2]), nitrogen deposition and forest management are under debate. We attributed the European carbon sink in forests using ORCHIDEE-FM, a process-based vegetation model that differs from earlier versions of ORCHIDEE by its explicit representation of stand growth and idealized forest management. The model was applied on a grid across Europe to simulate changes in the net ecosystem productivity (NEP) of forests with and without changes in climate, [CO2] and age structure, the three drivers represented in ORCHIDEE-FM. The model simulates carbon stocks and volume increment that are comparable – RMSE of 2 m3 ha-1 yr-1 and 1.7 kgC m-2 respectively – with inventory-derived estimates at country level for 20 European countries. Our simulations estimate a mean European forest NEP of 175 ± 52 gC m-2 yr-1 in the 1990s. The model simulation that is most consistent with inventory records provides an upwards trend of forest NEP of 1 ± 0.5 gC m-2 yr-2 between 1950 and 2000 across the EU 25. Further, the method used for reconstructing past age structure was found to dominate its contribution to temporal trends in NEP. The potentially large fertilizing effect of nitrogen deposition cannot be told apart as the model does not explicitly simulate the nitrogen cycle. Among the three drivers that were considered in this study, the fertilizing effect of increasing [CO2] explains about 61% of the simulated trend, against 26% to changes in climate, and 13% only to changes in forest age structure. The major role of [CO2] at the continental scale is due to its homogeneous impact on NPP. At the local scale, however, changes in climate and forest age structure often dominate trends in NEP by affecting NPP and heterotrophic respiration.” Valentin Bellassen, Nicolas Viovy, Sebastiaan Luyssaert, Guerric Le Maire, Mart-Jan Schelhaas, Philippe Ciais, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02476.x.

Snow cover has generally decreased in Arctic

The Changing Cryosphere: Pan-Arctic Snow Trends (1979–2009) – Liston & Hiemstra (2011) “Arctic snow presence, absence, properties, and water amount are key components of Earth’s changing climate system that incur far-reaching physical and biological ramifications. Recent dataset and modeling developments permit relatively high-resolution (10 km horizontal grid; 3 hour time-step) pan-Arctic snow estimates for 1979–2009. Using MicroMet and SnowModel in conjunction with land cover, topography, and 30 years of NASA-MERRA atmospheric reanalysis data, we created a distributed snow-related dataset including air temperature, snow precipitation, snow-season timing and length, maximum snow water equivalent depth (SWE), average snow density, snow sublimation, and rain-on-snow events. Regional variability is a dominant feature of the modeled snow-property trends. Both positive and negative regional trends are distributed throughout the pan-Arctic domain, featuring, for example, spatially distinct areas of increasing and decreasing SWE or snow season length. In spite of strong regional variability, the data clearly show a general snow decrease throughout the Arctic: maximum winter SWE has decreased, snow cover onset is later, the snow-free date in spring is earlier, and snow cover duration has decreased. The domain-averaged air temperature trend when snow was on the ground was 0.17 °C decade−1 with minimum and maximum regional trends of −0.55 and 0.78 °C decade−1, respectively. The trends for total number of snow days in a year averaged −2.49 days decade−1 with minimum and maximum regional trends of −17.21 and 7.19 days decade−1, respectively. The average trend for peak SWE in a snow season was −0.17 cm decade−1 with minimum and maximum regional trends of −2.50 and 5.70 cm decade−1, respectively.” Glen E. Liston, Christopher A. Hiemstra, Journal of Climate 2011, doi: 10.1175/JCLI-D-11-00081.1.

New analysis of climate in medieval times

Spatial and Temporal Characteristics of Climate in Medieval Times Revisited – Diaz et al. (2011) “Development of accurate reconstructions of past climate regimes, and enhancing our understanding of the causal factors that may have contributed to their occurrence is important for a number of reasons; these include improvements in the attribution of climate change to natural and anthropogenic forcing, gaining a better appreciation for the range and magnitude of low frequency variability and previous climatic regimes in comparison with the modern instrumental period, and developing greater insights into the relationship between human society and climatic changes. Here, we examine up-to-date evidence regarding the characteristics of the climate in medieval times (~ 950 to 1400 A.D.). Long and high-resolution climate proxy records reported in the scientific literature, which form the basis for the climate reconstructions, have greatly expanded in the last few decades, with greater numbers of sites that now cover more areas of the globe. Some comparisons with the modern climate record and discussion on potential mechanisms associated with the patterns of medieval climate are presented here, but our main goal is to provide the reader with some appreciation of the richness of past natural climate variability in terms of its spatial and temporal characteristics.” Henry F. Diaz, Ricardo Trigo, Malcolm K. Hughes, Michael E. Mann, Elena Xoplaki, and David Barriopedro, Bulletin of the American Meteorological Society 2011, doi: 10.1175/BAMS-D-10-05003.1. [Full text]

Potential climate tipping elements in Europe

Potential climatic transitions with profound impact on Europe Review of the current state of six ‘tipping elements of the climate system’ – Levermann et al. (2011) “We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding.” Anders Levermann, Jonathan L. Bamber, Sybren Drijfhout, Andrey Ganopolski, Winfried Haeberli, Neil R. P. Harris, Matthias Huss, Kirstin Krüger, Timothy M. Lenton and Ronald W. Lindsay, et al., Climatic Change, DOI: 10.1007/s10584-011-0126-5. [Full text]


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New improved AGW Observer!

Posted by Ari Jokimäki on June 24, 2011

I made some changes here:

– Page “about” was outdated so I edited the text there. I also added some things.

– I took out the usage of the term “denialist”. It’s not really necessary and some people find it offensive, so better to take it out even if it is quite descriptive term relating to some of the public “debate” on the climate issues. Category denialist claims was changed to climate claims and similar change was made to one heading in Article page.

That’s it. Have a nice summer (NH) and winter (SH).

Posted in General | 2 Comments »

New research from last week 24/2011

Posted by Ari Jokimäki on June 20, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Different retreat rates of Greenland outlet glaciers

Mass balance of Greenland’s three largest outlet glaciers, 2000–2010 – Howat et al. (2011) “Acceleration of Greenland’s three largest outlet glaciers, Helheim, Kangerdlugssuaq and Jakobshavn Isbræ, accounted for a substantial portion of the ice sheet’s mass loss over the past decade. Rapid changes in their discharge, however, make their cumulative mass-change uncertain. We derive monthly mass balance rates and cumulative balance from discharge and surface mass balance (SMB) rates for these glaciers from 2000 through 2010. Despite the dramatic changes observed at Helheim, the glacier gained mass over the period, due primarily to the short-duration of acceleration and a likely longer-term positive balance. In contrast, Jakobshavn Isbræ lost an equivalent of over 11 times the average annual SMB and loss continues to accelerate. Kangerdlugssuaq lost over 7 times its annual average SMB, but loss has returned to the 2000 rate. These differences point to contrasts in the long-term evolution of these glaciers and the danger in basing predictions on extrapolations of recent changes.” Howat, I. M., Y. Ahn, I. Joughin, M. R. van den Broeke, J. T. M. Lenaerts, and B. Smith (2011), Geophys. Res. Lett., 38, L12501, doi:10.1029/2011GL047565. [Full text]

Future changes in GHG global warming potentials

Future changes in global warming potentials under representative concentration pathways – Reisinger et al. (2011) “Global warming potentials (GWPs) are the metrics currently used to compare emissions of different greenhouse gases under the United Nations Framework Convention on Climate Change. Future changes in greenhouse gas concentrations will alter GWPs because the radiative efficiencies of marginal changes in CO2, CH4 and N2O depend on their background concentrations, the removal of CO2 is influenced by climate–carbon cycle feedbacks, and atmospheric residence times of CH4 and N2O also depend on ambient temperature and other environmental changes. We calculated the currently foreseeable future changes in the absolute GWP of CO2, which acts as the denominator for the calculation of all GWPs, and specifically the GWPs of CH4 and N2O, along four representative concentration pathways (RCPs) up to the year 2100. We find that the absolute GWP of CO2 decreases under all RCPs, although for longer time horizons this decrease is smaller than for short time horizons due to increased climate–carbon cycle feedbacks. The 100-year GWP of CH4 would increase up to 20% under the lowest RCP by 2100 but would decrease by up to 10% by mid-century under the highest RCP. The 100-year GWP of N2O would increase by more than 30% by 2100 under the highest RCP but would vary by less than 10% under other scenarios. These changes are not negligible but are mostly smaller than the changes that would result from choosing a different time horizon for GWPs, or from choosing altogether different metrics for comparing greenhouse gas emissions, such as global temperature change potentials.” Andy Reisinger, Malte Meinshausen and Martin Manning, Environ. Res. Lett. 6 024020 doi: 10.1088/1748-9326/6/2/024020. [Full text]

Review of stratospheric temperature trends

Stratospheric temperature trends: our evolving understanding – Seidel et al. (2011) “We review the scientific literature since the 1960s to examine the evolution of modeling tools and observations that have advanced understanding of global stratospheric temperature changes. Observations show overall cooling of the stratosphere during the period for which they are available (since the late 1950s and late 1970s from radiosondes and satellites, respectively), interrupted by episodes of warming associated with volcanic eruptions, and superimposed on variations associated with the solar cycle. There has been little global mean temperature change since about 1995. The temporal and vertical structure of these variations are reasonably well explained by models that include changes in greenhouse gases, ozone, volcanic aerosols, and solar output, although there are significant uncertainties in the temperature observations and regarding the nature and influence of past changes in stratospheric water vapor. As a companion to a recent WIREs review of tropospheric temperature trends, this article identifies areas of commonality and contrast between the tropospheric and stratospheric trend literature. For example, the increased attention over time to radiosonde and satellite data quality has contributed to better characterization of uncertainty in observed trends both in the troposphere and in the lower stratosphere, and has highlighted the relative deficiency of attention to observations in the middle and upper stratosphere. In contrast to the relatively unchanging expectations of surface and tropospheric warming primarily induced by greenhouse gas increases, stratospheric temperature change expectations have arisen from experiments with a wider variety of model types, showing more complex trend patterns associated with a greater diversity of forcing agents.” Dian J. Seidel, Nathan P. Gillett, John R. Lanzante, Keith P. Shine, Peter W. Thorne, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.125.

Evidence for ice shelf break-up in the past in Antarctica

Geological record of ice shelf break-up and grounding line retreat, Pine Island Bay, West Antarctica – Jakobsson et al. (2011) “The catastrophic break-ups of the floating Larsen A and B ice shelves (Antarctica) in 1995 and 2002 and associated acceleration of glaciers that flowed into these ice shelves were among the most dramatic glaciological events observed in historical time. This raises a question about the larger West Antarctic ice shelves. Do these shelves, with their much greater glacial discharge, have a history of collapse? Here we describe features from the seafloor in Pine Island Bay, West Antarctica, which we interpret as having been formed during a massive ice shelf break-up and associated grounding line retreat. This evidence exists in the form of seafloor landforms that we argue were produced daily as a consequence of tidally influenced motion of mega-icebergs maintained upright in an iceberg armada produced from the disintegrating ice shelf and retreating grounding line. The break-up occurred prior to ca. 12 ka and was likely a response to rapid sea-level rise or ocean warming at that time.” Martin Jakobsson, John B. Anderson, Frank O. Nitsche, Julian A. Dowdeswell, Richard Gyllencreutz, Nina Kirchner, Rezwan Mohammad, Matthew O’Regan, Richard B. Alley, Sridhar Anandakrishnan, Björn Eriksson, Alexandra Kirshner, Rodrigo Fernandez, Travis Stolldorf, Rebecca Minzoni and Wojciech Majewski, Geology, v. 39 no. 7 p. 691-694, doi: 10.1130/G32153.1.

Measuring atmospheric water vapor with cheap IR thermometer

Measuring Total Column Water Vapor by Pointing an Infrared Thermometer at the Sky – Mims et al. (2011) “A 2-year study affirms that the temperature indicated by an inexpensive ($20 to $60) IR thermometer pointed at the cloud-free zenith sky (Tz) is a proxy for total column water vapor (precipitable water or PW). Tz was measured at or near solar noon, and occasionally at night, from 8 September 2008 to 18 October 2010 at a field in South-Central Texas. PW was measured by a MICROTOPS II sun photometer. The coefficient of correlation (r2) of PW and Tz was 0.90, and the rms difference was 3.2 mm. A comparison of Tz with PW from a GPS site 31 km NNE yielded an r2 of 0.79, and an rms difference of 5.8 mm. An expanded study compared Tz from eight IR thermometers with PW at various times during the day and night from 17 May to 18 October 2010, mainly at the Texas site and 10 days at Hawaii’s Mauna Loa Observatory. The best results were provided by two IR thermometers that yielded an r2 of 0.96 and an rms difference with PW of 2.7 mm. The results of both the ongoing 2-year study and the 5-month comparison show that IR thermometers can measure PW with an accuracy (rms difference/mean PW) approaching 10%, the accuracy typically ascribed to sun photometers. The simpler IR method, which works day and night, can be easily mastered by students, amateur scientists and cooperative weather observers.” Forrest M. Mims III, Lin Hartung Chambers, David R. Brooks, Bulletin of the American Meteorological Society 2011. [Full text]

Growing frost flowers in the lab

Frost flowers in the laboratory: Growth, characteristics, aerosol, and the underlying sea ice – Roscoe et al. (2011) “In the laboratory, we have investigated the growth and composition of frost flowers. Their ionic composition has shown little difference from those of field measurements. Young frost flowers grown on sea ice are saline, leading us to speculate that wicking occurs continually during their growth on sea ice. The surface area of frost flowers is only a little larger than the area of ice underneath, consistent with recent field measurements from the Arctic. Time-lapse photography has allowed us to observe the extreme mobility of freshly forming sea ice, at the stage at which the mush has become rather solid, and continuing while the flowers grow. This mobility results in new brine being expelled to the surface, which therefore remains wet. During various stages of frost flower growth, we observed their freshly formed dendritic parts rapidly diminishing in size after contacting the surface, consistent with repeated wicking. Frost flowers proved to be very stable in the presence of wind, such that no aerosol was observed when wind was blown across them in the laboratory chamber. This is consistent with recent field observations of frost flowers coexisting with wind-blown snow.” Roscoe, H. K., B. Brooks, A. V. Jackson, M. H. Smith, S. J. Walker, R. W. Obbard, and E. W. Wolff (2011), J. Geophys. Res., 116, D12301, doi:10.1029/2010JD015144.

Anaerobic oxidation prevents methane outgassing from Lake Tanganyika

What prevents outgassing of methane to the atmosphere in Lake Tanganyika? – Durisch-Kaiser et al. (2011) “Tropical East African Lake Tanganyika hosts the Earth’s largest anoxic freshwater body. The entire water column holds over 23 Tg of the potent greenhouse gas methane (CH4). Methane is formed under sulphate-poor conditions via carbon dioxide reduction or fermentation from detritus and relict sediment organic matter. Permanent density stratification supports an accumulation of CH4 below the permanent oxycline. Despite CH4 significance for global climate, anaerobic microbial consumption of CH4 in freshwater is poorly understood. Here we provide evidence for intense methanotrophic activity not only in the oxic but also in the anoxic part of the water column of Lake Tanganyika. We measured CH4, 13C of dissolved CH4, dissolved oxygen (O2), sulphate (SO42-), sulphide (HS) and the transient tracers chlorofluorocarbon-12 (CFC-12) and tritium (3H). A basic one-dimensional model, which considers vertical transport and biogeochemical fluxes and transformations, was used to interpret the vertical distribution of these substances. The results suggest that the anaerobic oxidation of CH4 is an important mechanism limiting CH4 to the anoxic zone of Lake Tanganyika. The important role of the anaerobic oxidation for CH4 concentrations is further supported by high abundances (up to ∼33% of total DAPI-stained cells) of single living archaea, identified by fluorescence in situ hybridization.” Durisch-Kaiser, E., M. Schmid, F. Peeters, R. Kipfer, C. Dinkel, T. Diem, C. J. Schubert, and B. Wehrli (2011), J. Geophys. Res., 116, G02022, doi:10.1029/2010JG001323.

What takes volcanoes a whole year mankind does in just a few days

Human Activities Emit Way More Carbon Dioxide Than Do Volcanoes – AGU news article “On average, human activities put out in just three to five days the equivalent amount of carbon dioxide that volcanoes produce globally each year. So concludes a scientist who reviewed five published studies of present-day global volcanic carbon dioxide emissions and compared those emissions to anthropogenic (human-induced) carbon dioxide output.” AGU Release No. 11–22, 14 June 2011.

Europe cold winter 2009-2010: extreme NAO but relatively warm

European cold winter 2009–2010: How unusual in the instrumental record and how reproducible in the ARPEGE-Climat model? – Ouzeau et al. (2011) “Boreal winter 2009–2010 made headlines for cold anomalies in many countries of the northern mid-latitudes. Northern Europe was severely hit by this harsh winter in line with a record persistence of the negative phase of the North Atlantic Oscillation (NAO). In the present study, we first provide a wider perspective on how unusual this winter was by using the recent 20th Century Reanalysis. A weather regime analysis shows that the frequency of the negative NAO was unprecedented since winter 1939–1940, which is then used as a dynamical analog of winter 2009–2010 to demonstrate that the latter might have been much colder without the background global warming observed during the twentieth century. We then use an original nudging technique in ensembles of global atmospheric simulations driven by observed sea surface temperature (SST) and radiative forcings to highlight the relevance of the stratosphere for understanding if not predicting such anomalous winter seasons. Our results demonstrate that an improved representation of the lower stratosphere is necessary to reproduce not only the seasonal mean negative NAO signal, but also its intraseasonal distribution and the corresponding increased probability of cold waves over northern Europe.” Ouzeau, G., J. Cattiaux, H. Douville, A. Ribes, and D. Saint-Martin (2011), Geophys. Res. Lett., 38, L11706, doi:10.1029/2011GL047667.

Climate change causes concrete to deteriorate more rapidly

Impact of climate change on corrosion and damage to concrete infrastructure in Australia – Wang et al. (2011) “The durability of concrete is determined largely by its deterioration over time which is affected by the environment. Climate change may alter this environment, causing an acceleration of deterioration processes that will affect the safety and serviceability of concrete infrastructure in Australia, U.S., Europe, China and elsewhere. This investigation of concrete deterioration under changing climate in Australia uses Monte-Carlo simulation of results from General Circulation Models (GCMs) and considers high greenhouse gas emission scenarios representing the A1FI schemes of the IPCC. We present the implications of climate change for the durability of concrete structures, in terms of changes in probability of reinforcement corrosion initiation and corrosion induced damage at a given calendar year between 2000 and 2100 across Australia. Since the main driver to increased concrete deterioration is CO2 concentration and temperature, then increases in damage risks observed in Australia are likely to be observed in other concrete infrastructure internationally. The impact of climate change on the deterioration cannot be ignored, but can be addressed by new approaches in design. Existing concrete structures, for which design has not considered the effects of changing climate may deteriorate more rapidly than originally planned.” Xiaoming Wang, Mark G. Stewart and Minh Nguyen, Climatic Change, DOI: 10.1007/s10584-011-0124-7.

Summer snowfall decreases in Arctic because it changes to rain

Declining summer snowfall in the Arctic: causes, impacts and feedbacks – Screen & Simmonds (2011) “Recent changes in the Arctic hydrological cycle are explored using in situ observations and an improved atmospheric reanalysis data set, ERA-Interim. We document a pronounced decline in summer snowfall over the Arctic Ocean and Canadian Archipelago. The snowfall decline is diagnosed as being almost entirely caused by changes in precipitation form (snow turning to rain) with very little influence of decreases in total precipitation. The proportion of precipitation falling as snow has decreased as a result of lower-atmospheric warming. Statistically, over 99% of the summer snowfall decline is linked to Arctic warming over the past two decades. Based on the reanalysis snowfall data over the ice-covered Arctic Ocean, we derive an estimate for the amount of snow-covered ice. It is estimated that the area of snow-covered ice, and the proportion of sea ice covered by snow, have decreased significantly. We perform a series of sensitivity experiments in which inter-annual changes in snow-covered ice are either unaccounted for, or are parameterized. In the parameterized case, the loss of snow-on-ice results in a substantial decrease in the surface albedo over the Arctic Ocean, that is of comparable magnitude to the decrease in albedo due to the decline in sea ice cover. Accordingly, the solar input to the Arctic Ocean is increased, causing additional surface ice melt. We conclude that the decline in summer snowfall has likely contributed to the thinning of sea ice over recent decades. The results presented provide support for the existence of a positive feedback in association with warming-induced reductions in summer snowfall.” James A. Screen and Ian Simmonds, Climate Dynamics, DOI: 10.1007/s00382-011-1105-2.

Review on biodiversity refugia

Refugia: identifying and understanding safe havens for biodiversity under climate change – Keppel et al. (2011) “Aim  Identifying and protecting refugia is a priority for conservation under projected anthropogenic climate change, because of their demonstrated ability to facilitate the survival of biota under adverse conditions. Refugia are habitats that components of biodiversity retreat to, persist in and can potentially expand from under changing environmental conditions. However, the study and discussion of refugia has often been ad hoc and descriptive in nature. We therefore: (1) provide a habitat-based concept of refugia, and (2) evaluate methods for the identification of refugia.
Location  Global.
Methods  We present a simple conceptual framework for refugia and examine the factors that describe them. We then demonstrate how different disciplines are contributing to our understanding of refugia, and the tools that they provide for identifying and quantifying refugia.
Results  Current understanding of refugia is largely based on Quaternary phylogeographic studies on organisms in North America and Europe during significant temperature fluctuations. This has resulted in gaps in our understanding of refugia, particularly when attempting to apply current theory to forecast anthropogenic climate change. Refugia are environmental habitats with space and time dimensions that operate on evolutionary time-scales and have facilitated the survival of biota under changing environmental conditions for millennia. Therefore, they offer the best chances for survival under climate change for many taxa, making their identification important for conservation under anthropogenic climate change. Several methods from various disciplines provide viable options for achieving this goal.
Main conclusions  The framework developed for refugia allows the identification and description of refugia in any environment. Various methods provide important contributions but each is limited in scope; urging a more integrated approach to identify, define and conserve refugia. Such an approach will facilitate better understanding of refugia and their capacity to act as safe havens under projected anthropogenic climate change.” Gunnar Keppel, Kimberly P. Van Niel, Grant W. Wardell-Johnson, Colin J. Yates, Margaret Byrne, Ladislav Mucina, Antonius G. T. Schut, Stephen D. Hopper, Steven E. Franklin, Global Ecology and Biogeography, DOI: 10.1111/j.1466-8238.2011.00686.x.

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The climate commitment of new Finnish government

Posted by Ari Jokimäki on June 17, 2011

Looks like Finland is finally getting a new government after long negotiations. Here are the relevant sections regarding climate change of the negotiation result of the new Finnish government (link is to a Finnish text) translated by me quickly and roughly. First, in the summary they say:

Environment will be left in better shape to future generations. Finland will be reformed as a forerunner in nourishing biodiversity and preventing climate change. The goals of the government are to make future Finland a carbon neutral society, to make Finland a number one country in environmental technology, and to develop Finland into a most knowledgeable nation on environment.

Then, section 9 deals with climate policy:

Finland will participate actively to the international co-operation for solving the environmental challenges.

In UN level the goal is to have a cogent and effective climate treaty, which takes biodiversity and other goals of sustainable development into consideration, and which limits the global warming to two degrees.

It will be investigated what effects the EU goal of 30 % emission cuts from 1990 level by 2020 would have. The investigation will find out the effects of changing the goal to costs, society, competitiveness, and compatibility with the two degree goal considering other commitments of EU countries. By the end of 2012 the government decides to support the 30 % goal if the investigation qualifies it.

The government will advance the achieving of the energy efficiency goals of EU determinedly. In 2013 progress in Finland will be evaluated in order to decide of possible additional actions.

The most cost-effecient way to proceed towards 80% emission cuts by 2050 is to steer the investments of energy production and use towards the improvement of energy efficiency and utilization of renewable energy in early stage. The effects to economy, to employment, and to distribution of wealth will be investigated during the preparation and decision-making of climate politics.

In order to achieve the climate goals, the government will make a long term EU strategy of climate policy. Finland should influence the policy decisions of European union in such a way, that the competitive status of the actors under European Union stays reasonable compared to the competitive status of the external actors and that the internal competitive situation of European Union will not be distorted.

The government will advance the chances of Finland to survive and gain from the coming energy and climate challenges. By investing to the research, development and application of climate and environmental technology and also to the services and know-how in the field the chances of Finland to become the heading country in low emission solutions will be improved. The co-operation with Nordic countries will be strengthened in the field of climate policy.

In EU Finland will support the carbon sink calculation methods, which are based on scientifically determine monitoring of true changes in carbon sinks, and which secures the sustainable economical use of forests. The goal is to have a fair system of global climate change prevention.

The government acknowledges the uneven distribution of climate change effects globally and the probelmatic relation of climate change and poverty. Finland will participate the international climate funding according to its commitments. The government supports the coordination of climate policy with development policy and explores the chances to take innovative funding instruments into use in climate policy.

Government will set a ministrial working group to update the national climate and energy strategy by the end of 2012. According to the future briefing of climate and energy policy, a multidisclipinary and independent climate panel will be formed to follow the actualization and effectiveness of the strategy. The climate panel will prepare directional emission budgets for government, which will aid towards long term sustainable emission levels. The climate panel will advice government in defining and checking of the emission budgets, monitors them to be taken in use, and gives recommendations on actions to reduce emissions. By gained experience and investigations the government will prepare a bill and makes separate decision to set a climate law to steer the reductions of emissions that are outside the emissions trading.

Posted in Adaptation & Mitigation | 1 Comment »

New research from last week 23/2011

Posted by Ari Jokimäki on June 13, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Excellent suggestions from Alan Betts

A Proposal for Communicating Science – Betts (2011) “I suggest authors must submit for review, and scientific societies be obliged to publish two versions of every journal. One would be the standard journal in scientific English for their scientific club. The second would be a parallel open-access summary translation into plain English of the relevance and significance of each paper for everyone else.” Alan Betts, Bulletin of the American Meteorological Society 2011, doi: 10.1175/BAMS-D-11-00036.1. [full text]

Research synthesis on Arctic sea ice

The Arctic’s rapidly shrinking sea ice cover: a research synthesis – Stroeve et al. (2011) “The sequence of extreme September sea ice extent minima over the past decade suggests acceleration in the response of the Arctic sea ice cover to external forcing, hastening the ongoing transition towards a seasonally open Arctic Ocean. This reflects several mutually supporting processes. Because of the extensive open water in recent Septembers, ice cover in the following spring is increasingly dominated by thin, first-year ice (ice formed during the previous autumn and winter) that is vulnerable to melting out in summer. Thinner ice in spring in turn fosters a stronger summer ice-albedo feedback through earlier formation of open water areas. A thin ice cover is also more vulnerable to strong summer retreat under anomalous atmospheric forcing. Finally, general warming of the Arctic has reduced the likelihood of cold years that could bring about temporary recovery of the ice cover. Events leading to the September ice extent minima of recent years exemplify these processes.” Julienne C. Stroeve, Mark C. Serreze, Marika M. Holland, Jennifer E. Kay, James Malanik and Andrew P. Barrett, Climatic Change, DOI: 10.1007/s10584-011-0101-1. [full text]

Many areas are entering permanent heat regime in next few decades

Observational and model evidence of global emergence of permanent, unprecedented heat in the 20th and 21st centuries – Diffenbauch & Scherer (2011) “Given the severe impacts of extreme heat on natural and human systems, we attempt to quantify the likelihood that rising greenhouse gas concentrations will result in a new, permanent heat regime in which the coolest warm-season of the 21st century is hotter than the hottest warm-season of the late 20th century. Our analyses of global climate model experiments and observational data reveal that many areas of the globe are likely to permanently move into such a climate space over the next four decades, should greenhouse gas concentrations continue to increase. In contrast to the common perception that high-latitude areas face the most accelerated response to global warming, our results demonstrate that in fact tropical areas exhibit the most immediate and robust emergence of unprecedented heat, with many tropical areas exhibiting a 50% likelihood of permanently moving into a novel seasonal heat regime in the next two decades. We also find that global climate models are able to capture the observed intensification of seasonal hot conditions, increasing confidence in the projection of imminent, permanent emergence of unprecedented heat.” Noah S. Diffenbaugh and Martin Scherer, Climatic Change, DOI: 10.1007/s10584-011-0112-y. [full text]

Warming climate is a threat to platybus

Early response of the platypus to climate warming – Klamt et al. (2011) “Combining a climatic envelope modeling technique with more than two centuries (1800-2009) of distribution records has revealed the effects of a changing climate on the egg-laying monotreme, the platypus, Ornithorhynchus anatinus. We show that the main factor associated with platypus occurrence switched from aquatic habitat availability (estimated by rainfall) to thermal tolerances (estimated by annual maximum temperature) in the 1960’s. This correlates directly with the change in the annual maximum temperature anomaly from cooler to warmer conditions in southeastern Australia. Modeling of platypus habitat under emission scenarios (A1B, A2, B1 and B2) revealed large decreases (> 30%) in thermally suitable habitat by 2070. This reduction, compounded by increasing demands for water for agriculture and potable use, suggests that there is real cause for concern over the future status of this species, and highlights the need for restoration of thermal refugia within the platypus’ modeled range.” Melissa Klamt, Ross Thompson, Jenny Davis, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02472.x.

Rapid melt has started in Canada’s Arctic ice caps

Extreme melt on Canada’s Arctic ice caps in the 21st century – Sharp et al. (2011) “Canada’s Queen Elizabeth Islands contain ∼14% of Earth’s glacier and ice cap area. Snow accumulation on these glaciers is low and varies little from year to year. Changes in their surface mass balance are driven largely by changes in summer air temperatures, surface melting and runoff. Relative to 2000–2004, strong summer warming since 2005 (1.1 to 1.6°C at 700 hPa) has increased summer mean ice surface temperatures and melt season length on the major ice caps in this region by 0.8 to 2.2°C and 4.7 to 11.9 d respectively. 30–48% of the total mass lost from 4 monitored glaciers since 1963 has occurred since 2005. The mean rate of mass loss from these 4 glaciers between 2005 and 2009 (−493 kg m−2 a−1) was nearly 5 times greater than the 1963–2004 average. In 2007 and 2008, it was 7 times greater (−698 kg m−2 a−1). These changes are associated with a summer atmospheric circulation configuration that favors strong heat advection into the Queen Elizabeth Islands from the northwest Atlantic, where sea surface temperatures have been anomalously high.” Sharp, M., D. O. Burgess, J. G. Cogley, M. Ecclestone, C. Labine, and G. J. Wolken (2011), Geophys. Res. Lett., 38, L11501, doi:10.1029/2011GL047381.

Clear warming in Arabian Peninsula

Recent observed climate change over the Arabian Peninsula – AlSarmi & Washington (2011) “We have examined trends in temperature and precipitation parameters for the Arabian Peninsula (AP) during the last 2 to 3 decades. The data set has been carefully quality controlled and checked for homogeneity. Although of low density (21 stations) and relatively short time period, a clear picture of climate change in the region has emerged. The general pattern of the AP mean annual temperature trend is one of warming, with 14 of 21 stations show statistically significant warming at 0.05 level and most at 0.001 level and only one (Seeb) showing statistically significant cooling. The highest statistically significant mean annual warming trends are found in Oman (Sur = 1.03°C decade−1) and Emirates (Dubai = 0.81°C decade−1). The season of maximum warming in mean temperature is March to April. The highest monthly mean temperature trend in the AP occurs in Sur in May (1.47°C decade−1). There is a broad statistically significant increase in mean annual maximum temperature in AP in 12 out of 21 stations, with the highest trends in central and eastern/southeastern AP. Only SW AP and the Gulf of Oman do not show warming. The highest monthly maximum temperature trend in the AP occurs in Bahrain in March (2.27°C decade−1). The second highest significant warming trends are reported in Doha in February (1.54°C decade−1). For minimum temperature, 16 out of 21 stations show statistically significant warming trends, with the highest annual trends observed in the Emirates (Dubai = 1.24°C decade−1), northwest Oman (Sohar = 1.17°C decade−1) and Qatar (Doha = 1.13°C decade−1). The highest monthly minimum temperature warming rate occurred in October. Both Dubai and Kuwait reported the highest significant rate of 2.00°C decade−1. The general mean annual diurnal temperature range trend is negative in the AP, with six out of 21 stations show statistically significant negative trends while three stations show statistically significant positive trends. Trends in mean annual precipitation are significant at only two stations which show a decrease in precipitation.” AlSarmi, S., and R. Washington (2011), J. Geophys. Res., 116, D11109, doi:10.1029/2010JD015459.

Climate change increases dust over Mongolia

Recent increasing trend in dust frequency over Mongolia and Inner Mongolia regions and its association with climate and surface condition change – Lee & Sohn (2011) “Trends in dust events over China and Mongolia were examined using 34 years (1974–2007) of visibility data over dust source regions of China and 10 years (1998–2007) of dust reports from Synoptic Observations (SYNOP) stations over China and Mongolia. Dust occurrences in Mongolia and northern Inner Mongolia increased over the 1998–2007 SYNOP data period while most dust source regions of China experienced a continuous decrease over the 34-year data period. Increased dust occurrences in Mongolia as well as in Inner Mongolia appear to be caused by degraded surface vegetation and reduced soil moisture associated with intensified drought conditions after the mid-1990s. Results suggest that recent increases in dust events over Korea and Japan are linked to increased dust occurrences over Mongolia and Inner Mongolia.” Eun-Hee Lee and Byung-Ju Sohn, Atmospheric Environment, doi:10.1016/j.atmosenv.2011.05.065.

In Buenos Aires population grows but UHI decreases

Temporal variability of the Buenos Aires, Argentina, urban heat island – Camilloni & Barrucand (2011) “This paper describes the statistical characteristics and temporal variability of the urban heat island (UHI) intensity in Buenos Aires using 32-year surface meteorological data with 1-h time intervals. Seasonal analyses show that the UHI intensity is strongest during summer months and an “inverse” effect is found frequently during the afternoon hours of the same season. During winter, the UHI effect is in the minimal. The interannual trend and the seasonal variation of the UHI for the main synoptic hours for a longer record of 48 years are studied and associated to changes in meteorological factors as low-level circulation and cloud amount. Despite the population growth, it was found a negative trend in the nocturnal UHI intensity that could be explained by a decline of near clear-sky conditions, a negative trend in the calm frequencies and an increase in wind speed. Urban to rural temperature differences and rural temperatures are negatively correlated for diurnal and nocturnal hours both for annual and seasonal scales. This result is due to the lower interannual variability of urban temperatures in comparison to rural ones.” Inés Camilloni and Mariana Barrucand, Theoretical and Applied Climatology, DOI: 10.1007/s00704-011-0459-z.

Pacific winds have intensified possibly due to global warming

Evidence for strengthening of the tropical Pacific Ocean surface wind speed during 1979–2001 – Li & Ren (2011) “Using multiple surface wind speed (SWS) data sets and trend empirical orthogonal function analysis, we have explored the trend in SWS associated with the large-scale tropical Pacific atmospheric circulation for the period 1979–2001. The present research provides a robust evidence of strengthening of the tropical Pacific Ocean SWS during this period and the magnitude is generally in line with the finding of Wentz et al. The strengthening in SWS is closely associated with the so-called La Niña-like sea surface temperature (SST) trend pattern rather than the changes in the ENSO, ENSO Modoki, or PDO. The present results, together with those from some recent climate model simulations, suggest that global warming forcing may have caused an intensification of SWS in the tropical Pacific Ocean by inducing the La Niña-like SST trend pattern due to ocean dynamics. Meanwhile, the strengthening in the tropical Pacific Ocean surface trade winds may also feedback to enhance the La Niña-like SST trend pattern under the positive wind-upwelling dynamic feedback mechanism.” Gen Li and Baohua Ren, Theoretical and Applied Climatology, DOI: 10.1007/s00704-011-0463-3.

PETM carbon emissions were much slower than today

Slow release of fossil carbon during the Palaeocene–Eocene Thermal Maximum – Cui et al. (2011) “The transient global warming event known as the Palaeocene–Eocene Thermal Maximum occurred about 55.9 Myr ago. The warming was accompanied by a rapid shift in the isotopic signature of sedimentary carbonates, suggesting that the event was triggered by a massive release of carbon to the ocean–atmosphere system. However, the source, rate of emission and total amount of carbon involved remain poorly constrained. Here we use an expanded marine sedimentary section from Spitsbergen to reconstruct the carbon isotope excursion as recorded in marine organic matter. We find that the total magnitude of the carbon isotope excursion in the ocean–atmosphere system was about 4‰. We then force an Earth system model of intermediate complexity to conform to our isotope record, allowing us to generate a continuous estimate of the rate of carbon emissions to the atmosphere. Our simulations show that the peak rate of carbon addition was probably in the range of 0.3–1.7 Pg C yr−1, much slower than the present rate of carbon emissions.” Ying Cui, Lee R. Kump, Andy J. Ridgwell, Adam J. Charles, Christopher K. Junium, Aaron F. Diefendorf, Katherine H. Freeman, Nathan M. Urban & Ian C. Harding, Nature Geoscience, 2011, doi:10.1038/ngeo1179.

Thawing permafrost makes wetlands smaller

Reduction in areal extent of high-latitude wetlands in response to permafrost thaw – Avis et al. (2011) “Wetlands are vegetated regions that are inundated with water on a permanent, seasonal or intermittent basis. These ecosystems play an important role in the carbon cycle: wetlands take up and store carbon, and release carbon dioxide and methane through the decomposition of organic matter. More than 50% of wetlands are located in the high northern latitudes, where permafrost also prevails and exerts a strong control on wetland hydrology. Permafrost degradation is linked to changes in Arctic lakes: between 1973 and 2004 the abundance of lakes increased in continuous permafrost zones, but decreased in other zones. Here, we use a global climate model to examine the influence of permafrost thaw on the prevalence of high-latitude northern wetlands, under four emissions scenarios. We show that as permafrost degrades, the areal extent of wetlands declines; we found a net loss in wetland extent in the three highest emissions scenarios. We also note an initial increase in the number of days of the year conducive to wetland formation, owing to an increase in unfrozen surface moisture resulting from a lengthening of the thaw season. This is followed by a dramatic decline in the number of wetland-conducive days, owing to a deepening of the permafrost surface, and drainage of near-surface moisture to deeper soil layers. We suggest that a reduction in the areal extent and duration of wetlands will influence high-latitude carbon emissions.” Christopher A. Avis, Andrew J. Weaver & Katrin J. Meissner, Nature Geoscience, 2011, doi:10.1038/ngeo1160.

Posted in Climate science | 7 Comments »

Poleward motion of storm tracks

Posted by Ari Jokimäki on June 7, 2011

A new study analysing cloud cover measurements has noted storm tracks and the cloudiness related to them migrating polewards during the last few decades. Additionally storm tracks seem to have become narrower. Observed changes in cloudiness have an amplifying effect on global warming.

In mid-latidudes of both hemispheres there is a region where large scale atmospheric wave activity transfers heat and moisture polewards. This causes a band of low-pressure systems, where cloudiness and rainfall is common. These bands are called storm tracks. Storm tracks are an important part of weather system and they also have an effect on climate by their radiative cooling. They also have an effect on large scale weather patterns (for example on North Atlantic Oscillation and on El Niño).

Based on the simulations of climate models, storm tracks should move towards Earth poles when climate warms. However, the expected change is so small that it is still difficult to observe it at this time. Despite of numerous studies it is not clear exactly why the storm tracks move polewards in models. Greenhouse gas warming is probably one factor but also aerosols might be involved.

A new study seeks to find if the shifting of storm tracks is already evident in the cloud cover measurements of last few decades. Study used ISCCP (International Satellite Cloud Climatology Project) measurements between 1983 and 2008. During that time global surface temperature has risen about 0.5 degrees C, mich might be big enough for the detection of storm track shifting. Study also used data from some other sources (ERBE, CERES and MODIS). Additionally situation was simulated with climate models.

ISCCP problems

There are known errors in ISCCP data, of which particularly the changes in satellite viewing angle makes the interpretation of the data problematic. It seems that these days every new study using ISCCP data is also a study on satellite viewing angles. Satellite viewing angle changes, when a satellite is added to the satellite network, satellite location is changed, or a satellite is removed from the network. A change in the viewing angle affects the amount of measured cloudiness. A proper solution to the problem does not exist yet, but this study makes an effort to go around the problem with couple of different methods.

Easiest method for going around the problem is to leave out the data from those regions which are affected the most. The weakness of this method is that the problem still exists in other regions at least to some extent. In this study the region of Indian Ocean was left out because it was between the borders of the measuring areas of two satellites and there were no supporting data available from other satellites before 1997.

The effects of satellite network changes can be tried to remove by regression analysis. This method was used on the global cloud data over the oceans. After the correction, the decreasing cloud cover trend in ISCCP data got smaller from 1.5 % to 0.4 % per decade. In the storm track areas the effect of the correction is smaller.

Satellite viewing angle problems are especially bad in thin clouds, because they can easily fall out of detection limit after viewing angle change. It might be possible to reduce the problem by concentrating on thick clouds only, but this method has its own problems, and the method doesn’t give truthful picture of total cloudiness.

Shifting of storm tracks

Studied storm track regions show clear cloud maxima which can have over 90 % average annual cloud cover. Observations also show a poleward shifting of storm tracks during the last 25 years. Shifting has been stronger in the equator side of storm tracks, which has caused a narrowing of the storm tracks. All studied regions show similar changes in storm tracks. Narrowing of storm tracks is especially strong in the North Atlantic, which may suggest that the region is strongle infected by the satellite viewing angle problem, which also was to be expected beforehand.

In ISCCP data, storm tracks have shifted 0.15 – 0.17 degrees of latitude per decade in other regions except in North Atlantic, where again is anomalously large change (0.6 degrees of latitude per decade).

With storm track shifting there is an associated decrease in cloudiness in storm track areas. Observations show couple of percent decrease in cloudiness in storm track areas (and again North Atlantic has clearly bigger change). Most of the cloud cover decrease occurs in low clouds. Middle clouds and chigh clouds have even increased a little.

The climatic effect of storm track shifting

The changes in longwave and shortwave radiation (measured in ERBE and CERES projects) correlate with cloudiness sufficiently well, that the effect of clouds to radiative fluxes can be estimated from ISCCP data. In the case of shortwave radiation, clouds change the radiative flux by reflecting the radiation from the Sun back to space. The effect to shortwave radiation can be seen in the data especially in the storm track areas. Clouds affect the radiative flux of the longwave radiation through their greenhouse effect, which also is seen in the data.

Total cloudiness has decreased 2-3% in storm track areas. This has caused the reflected solar radiation to decrease, which means that in storm track areas more solar radiation reaches the Earth’s surface. This change causes a warming effect (of about 3 watts per square meter). Middle and high clouds have increased by 2-5%. This reduces the outgoing longwave radiation, which means that bigger part of longwave radiation stays on Earth and causes warming (of about 1 – 3 watts per square meter).

The changes in cloudiness cause a warming effect both by longwave and shortwave fluxes (total effect is about 3 – 5 watts per square meter). Therefore it seems that cloud changes in storm track areas have amplified global warming (this is so called positive feedback). However, this result doesn’t necessarily reflect the global situation, because possible compensating effects in other areas were not studied. Additionally, ISCCP data problems may contribute to the situation considerably. For example, without thin clouds even a small negative feedback is possible (total effect in this case is -1 – 2 watts per square meter, so even in this case the most probable value of feedback is positive, even if uncertainty bars allow the possibility of a small negative feedback).

20 climate models were investigated and seven of them showed poleward storm track shifting with global warming. However, the amount of shifting was considerably smaller than what ISCCP data shows. The models, where storm tracks shifted the most, meaning that they were closest to observations, climate sensitivity was greatest. Models with climate sensitivity less than 3 degrees Celsius don’t even show statistically significant storm track shifting in all storm track areas. This suggests that also model results support positive cloud feedback associated with storm tracks.

Reference: Frida A-M. Bender, V. Ramanathan and George Tselioudis, Changes in extratropical storm track cloudiness 1983–2008: observational support for a poleward shift, Climate Dynamics, DOI: 10.1007/s00382-011-1065-6. [abstract]

Additional information:

Viewing Angle on ISCCP Problems
Papers on Hadley Cell expansion

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New research from last week 22/2011

Posted by Ari Jokimäki on June 6, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

CO2 doubling at Triassic/Jurassic boundary

Extremely elevated CO2 concentrations at the Triassic/Jurassic boundary – Steinthorsdottir et al. (2011) “Although progress has been made in recent years in reconstructing the environmental conditions at the Triassic/Jurassic Boundary (TJB), published records of atmospheric CO2 concentrations have been of low resolution and/or based on multi-taxon estimates. This is addressed here by reconstructing CO2 concentrations across the TJB using stomatal frequencies of four phylogenetically and ecologically distinct plant groups from two depositionally, geographically and taphonomically seperate boundary sections in East Greenland and Northern Ireland, with stomatal proxy methods and regression analysis. The resulting CO2 records then are compared with an additional existing TJB record from a geological section in Sweden. The final results indicate that pre-TJB (Rhaetian), the CO2 concentration was appoximately 1000 ppm, that it started to rise steeply pre-boundary and had doubled to around 2000–2500 ppm at the TJB. The CO2 concentration then remained evelvated for some time post-boundary, before returning to pre-TJB levels in the Hettangian. These results are in very good accordance with published C-isotope, fire and leaf dissection records, and clearly indicate steeply rising and lingering CO2 concentration at the TJB.” Margret Steinthorsdottir, Andrew J. Jeram and Jennifer C. McElwain, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.05.050.

Spain is warming up

Spatial analysis of mean temperature trends in spain over the period 1961–2006 – del Rio et al. (2011) “The spatial distribution of recent mean temperature trends over Spain during the period 1961–2006 at monthly, seasonal and annual time scale is carry out in this study by applying various statistical tools to data from 473 weather stations. The magnitude of trends was derived from the slopes of the linear trends using ordinary least-square fitting. The non parametric Mann-Kendall test was used to determine the statistical significance of trends. Maps of surface temperature trends were generated by applying a geostatistical interpolation technique to visualize the detected tendencies. This study reveals that temperature has generally increased during all months and seasons of the year over the last four decades. More than 60% of whole Spain has evidenced significant positive trends in March, June, August, spring and summer. This percentage diminishes around 40% in April, May and December. Annual temperature has significantly risen in 100% of Spain of around 0.1-0.2 °C/decade according to the Fourth Assessment Report of the IPCC.” S. del Río, L. Herrero, C. Pinto-Gomes and A. Penas, Global and Planetary Change, doi:10.1016/j.gloplacha.2011.05.012.

Pliocene – similar CO2 but warmer than today

Climate and environment of a Pliocene warm world – Salzmann et al. (2011) “The Pliocene Epoch, 5.33 – 2.58 million years ago (Ma), was a generally warmer and wetter interval with atmospheric CO2-concentrations at or slightly above modern levels. This paper provides an overview of Pliocene vegetation, sea surface temperatures and climate modelling outcomes. Most prominent changes in Pliocene biome distribution compared to today include a northwards shift of temperate and boreal vegetation zones in response to a warmer and wetter climate as well as an expansion of tropical savannas and forests at the expense of deserts. Faunal analysis techniques and modelling experiments using the Hadley Centre climate model identified significantly higher Pliocene sea surface temperatures at mid and high latitudes of the northern hemisphere with cooling or unchanged sea surface temperatures at low latitudes. Global mean annual surface temperatures (MAT) are estimated to have been 2 to 3 °C higher during the Piacenzian (3.6-2.58 Ma) than today with a reduced equator to pole gradient. The marine realm during the Pliocene was characterised by a reconfiguration of ocean gateways, particularly the narrowing of the Indonesian Seaway and closure of the Central American Isthmus, which produced essentially a modern pattern of ocean circulation. In the Southern Ocean a warm early Pliocene gave way to late Piacenzian cooling. Proxy data indicate a reduced east to west sea surface temperature gradient in the tropical Pacific during the Pliocene warmth. The Pliocene is one of the most intensively studied geological intervals of the pre-Quaternary. No other warm period in the geological past yields such a unique combination of near modern atmospheric CO2-concentrations, palaeogeography and palaeobiology. However, this paper also identifies data gaps and shortcomings in the reconstruction of Pliocene environments using proxy data and climate models on which future research should focus.” Ulrich Salzmann, Mark Williams, Alan M. Haywood, Andrew L.A. Johnson, Sev Kender and Jan Zalasiewicz, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.05.044.

Global warming might show in North Atlantic tides

Rapid change in semi-diurnal tides in the North Atlantic since 1980 – Müller (2011) “An anomalously large trend of M2 and S2 amplitudes and phases, beginning in the early 1980s, is observed in the North Atlantic. Harmonic analysis of long-term sea-level records from tide-gauge stations along the North American Atlantic coast and European Atlantic coast shows a large decrease in M2 and S2 amplitudes and an increase in phase lag. The characteristics of the evolution of M2 and S2 tides are similar, but not fully conclusive, which may suggesting different causes. In general, the trends may be due to global warming, which significantly increased in the early 1980s in the North Atlantic region. Several climate-related driving mechanisms for the observed changes in tides are discussed.” Müller, M. (2011), Geophys. Res. Lett., 38, L11602, doi:10.1029/2011GL047312.

Annually resolved temperature reconstruction from 5Ma

Climate variability in the Early Pliocene Arctic: Annually resolved evidence from stable isotope values of sub-fossil wood, Ellesmere Island, Canada – Csank et al. (2011) “Tree-ring analyses have contributed significantly to investigations of past climate. Stable isotope climate proxies (δ18O, δD and δ13C values) enhance traditional ring-width data, although poor preservation of ancient wood has tended to limit development of stable isotope proxy records to the Holocene and the Late Pleistocene. Here we apply stable isotope techniques to wood that represent the remains of Mixed-Coniferous Boreal Vegetation preserved in Early Pliocene (4–5 Ma) deposits at Strathcona Fiord, Ellesmere Island, Canada (ca. 78°N). Four well-preserved tree trunks, identified through wood anatomical characteristics as Larix (larch), from this high Arctic site provide annually resolved sequences of up to 250 years from which we developed a high-resolution record of Pliocene climate. Stable oxygen isotope values, in conjunction with ring-width measurements were used to derive annually resolved temperature records for this site. Our ring-width and isotope-based reconstructions provide an annually resolved record, up to 250 years, of temperature and indicate growing season (JJ) temperatures (15.8 ± 5.0 °C) 11.8 ± 5.1 °C, and mean annual temperatures (MAT) (− 1.4 ± 4.0 °C) 18.3 ± 4.1 °C warmer than present. Estimated isotope values of precipitation of − 16.3 ± 2 ‰ (δ18O) and − 150.1 ± 8.9 ‰ (δD) were calculated from the isotopic values of wood cellulose. Relative humidity estimated from both δ13C and δD records ranged from 60-80%. Paleotemperature, source water and humidity estimates are comparable to those of a modern Boreal Forest growing ca. 15-20° south of modern Ellesmere Island.” A.Z. Csank, W.P. Patterson, B.M. Eglington, N. Rybczynski and J.F. Basinger, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.05.038.

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